Commercial, industrial, domestic and apartment buildings require ventilation, and it is common for the natural leakage around doors, wall-ceiling joints, etc. found in standard building construction to allow sufficient air to enter the building. A pressure drop from the exterior to the interior of the building can arise from many factors, such as high winds, exhaust fans and combustion air for fuel-burning furnaces. This tends to draw outside air into the building through any crack or opening.
The problem with the conventional approach is that the amount of ventilation air is not controlled, the temperature in the building near the outside walls is lower than average and less comfortable, and additional heat must be provided to heat the outside air to room temperature during the heating season.
This problem has typically been solved by installing gas, oil or electric heaters and air-moving fans to heat the incoming air. When solar panels are used to heat a building, air is recirculated from the building through the collector and back. During the heating season, the ambient temperature is lower than the room temperature, and therefore a recirculating solar collector operates at a much reduced efficiency level.
One of us has disclosed two methods and apparatus which avoid using consumable energy, like oil, to heat incoming air for a building. Instead of simply recirculating interior air from the building through a solar collector and back to the building, fresh make-up air for ventilation purposes is introduced into the building after first passing the air through a solar collector located on a south-facing wall of the building. In Canadian Pat. No. 1,196,825, issued Nov. 19, 1985, the solar collector consists of glazing over a darkened wall. In U.S. Pat. No. 4,774,932, issued Oct. 4, 1988, the solar collector consists of a darkened collector panel with corrugations running vertically, and collecting means for withdrawing the heated air from vertical grooves near the top of the panel.
The latter method is less expensive for accomplishing the same goal. Its efficiency in collecting the total heat created by the solar radiation in the collector panel can be reduced in some locations or on sloped walls. The air rising in the grooves heats up, becomes lighter and moves faster, and its initially laminar flow may turn into turbulent flow, mixing with cold air and losing heat to the outside. The taller the solar panel is, the more intensively the sun heats the panel, and the stronger a wind blows. The heat loss grows with the height of the panel as its temperature is highest at the top. This loss is aggravated if the panel does not have a selective coating.